The Subspace Network Whitepaper
In an effort to make blockchains more energy-efficient, egalitarian, and decentralized, several new protocols employ consensus based on Proofs-of-Capacity (PoC), which replace compute-intensive mining with storage-intensive farming. We observe that PoC consensus introduces a unique mechanism design challenge, referred to as the farmer’s dilemma, which suggests that existing constructions are not actually incentive compatible.
Simply put, farmers must decide whether to allocate scarce storage resources towards either maintaining the chain state and history or maximizing the amount of space they pledge towards consensus. Rational farmers will always choose the latter, at best becoming light clients, while at worst encouraging pooled farming under a few trusted operators. To resolve this dilemma, we introduce Subspace, a PoC blockchain in which farmers maintain neither the state nor the history, while retaining the security properties and decentralization benefits of a full node.
Consensus in Subspace is based on proofs of replicated storage of the history of the blockchain itself. Farmers store the history collectively, many times over, with each farmer storing as many replicas as their disk space allows. Consensus and computation are then decoupled, such that farmers only propose an ordering for transactions, while staked executor nodes maintain the state and compute transitions.
This separation of concerns significantly reduces the storage and compute overhead needed to operate a farmer, even in an Ethereum-style execution model, allowing for high levels of participation in consensus by ordinary users with commodity hardware.